1. Technical Field
The present invention relates to a navigation system for a vehicle that provides route planning and route guidance information.
2. Related Art
Navigation systems have become standard equipment on many vehicles. The navigation systems often include GPS systems that receive satellite radio signals that are used in triangulating the position of the vehicle. The GPS data also may be combined with other data provided by the vehicle to increase the accuracy with which the current position of the vehicle is determined. This other data may be provided by motion sensors, wheel sensors, and the like. The navigation system may display the current position of the vehicle on a map provided on a display screen within the field of view of the user.
Navigation systems allow for route planning and route guidance from the current position of the vehicle to a desired endpoint destination. To this end, navigation systems may be operated in a route planning mode and a route guidance mode. In the route planning mode, the user enters the desired endpoint destination. The endpoint destination is typically selected through user manipulation of a keyboard, a joystick-like device, a mouse-like device, etc.
Once a particular destination has been selected, the navigation system enters the route guidance mode. In this mode, a database is used to generate a route list. The route list, in turn, is used in combination with the current location of the vehicle to generate route guidance instructions. The route guidance instructions may be provided to the user on the display screen and/or acoustically using a human voice (recorded and/or synthesized). If the vehicle deviates from the predetermined route, the navigation system recalculates the route and provides new driving instructions.
The size of the display screen may limit the amount of information that can be provided to the user by the navigation system at any given time. In many instances, only primary information, such as the street network, route path through the street network, and maneuver points on the street network is provided on the display screen. The user may change only the section of the map that is displayed on the screen or the scale of the map during the route guidance mode. Other changes are inhibited because of the safety issues involved with manipulating the keyboard and/or mouse-like device used to make such changes. Consequently, the user cannot change various navigation system parameters or display other information once route guidance has begun.